Meaning: This phrase means that one is able to complete a difficult task with ease by knowing just where to focus the work. It is somewhat similar to the English expression, "like a hot knife through butter."
Source: Zhuangzi (Chuang-tzu), "The Secret of Caring for Life."
During the Warring States Period, King Hui employed a famous chef to carve up beef for him.
The chef worked quickly and smoothly, easily separating the skin and meat with little effort by cutting in at the joints-the knees, shoulders....
The king repeatedly praised the fine work of his chef. The chef explained to the king how he had acquired his carving skills.
The chef said, "When I first started out I knew nothing about the skeletal structure of cattle, and knew nothing about where to begin carving. But after three years, I knew the skeleton and joints like the palm of my own hand. Since then, I have been able to carve by relying on feel rather than by relying on my eyes."
"Ordinary chefs use their knives to hack through the bones, so they must change knives each month. But I carve by inserting a thin knife into the spaces between the bones, where there is naturally a lot of room to work. That's why this knife still looks as good as new even though I've been using it for 19 years."
King Hui found this story to be highly instructive. He quickly grasped the larger lesson that for each task, there is a proper place to "cut through" obstacles and complete the job with a minimum of effort.